OpenSprinkler › Forums › Hardware Questions › OpenSprinkler Pi (OSPi) › OpenSprinkler Pi Exhaust Fan – Sealed Case Cooling › Re: Re: OpenSprinkler Pi Exhaust Fan – Sealed Case Cooling
Remember that the OSPi’s power supply is 24 Volts AC. It derives it’s power and the power for the Raspberry Pi from this base supply. Most irrigation transformers provide about 1 – 1.25 Amps AC which is sufficient to run the electronics and switch two sprinkler valves (Master and one channel). Most fans for electronics use are designed to run from a DC supply. The DC for the electronics is provided by a LM2596 chip which, why adequately powerful to provide enough power, has been implemented on the board specifically to provide a fairly small amount of DC power.
There is no heat sink on the LM2596 so heat generation is a consideration. Further the electrical noise generated by many fans may cause problems for the Pi. Given this and the limited overall power available “within the box” I would recommend that any extra fans are powered by their own, separate power supply.